Radiometrics has been used for geological mapping and exploration since the early days of geophysics. Often large scale regional surveys are conducted by mounting a gamma-ray spectrometer in a plane and flying over the area in a grid at altitudes of about 80m elevation. Often a gamma-ray spectrometer is part of a suite of geophysical methods that are mounted in a aircraft.
Changes in lithology (rock type, provenance) are often accompanied by changes in the concentrations of the natural occurring radionuclides. The maps of the radionuclides can therefore be used as a good indicator of geological variations in the field and help a geologist to set up a detailed geological investigation.
Many mineral deposits have specific radiometric signatures. Hydrothermal ore deposits are often associated with potassium alteration (a mineral alteration is a change in the composition of the mineral) and ores containing uranium or thorium can be measured directly.